Mirror displays for digital signage or the like applications have been proposed which include a half mirror plate with a half mirror layer on the viewing surface side of a display device to function as a mirror. Such mirror displays provide images by display light emitted from the display devices and are also used as mirrors by reflecting external light.
For the half mirror layer, an optical member with reflective function is used, and known examples thereof include reflective polarizers such as a multilayer reflective polarizer. A reflective polarizer reflects, among incident light components, polarized light components that are parallel to the reflection axis and transmits polarized light components that are perpendicular to the reflection axis. Thus, a reflective polarizer can transmit light that is emitted from a display device as display light to the viewing surface side and reflect external light that is perpendicular to the polarization direction of the display light to the viewing surface side. Such a mirror display including a reflective polarizer as a half mirror layer switches between a display mode and a mirror mode by the use of such a principle.
Proposed examples of the display device include a liquid crystal display device that can be enlarged (for example, see Patent Literature 1) and a liquid crystal display device that surely achieves the visibility through polarized sunglasses at any screen orientation (for example, see Patent Literature 2).